Fiber-reinforced thermoplastic composite bonded to wood

ABSTRACT

The present invention relates to wood that is reinforced with a fiber-reinforced thermoplastic composite that contains a plurality of substantially parallel continuous fibers impregnated with thermoplastic polymer having the following structural units:                    
     where Z is S or O, and Z′ is S, O, N-alkyl or NH The invention is useful in a variety of applications including glue-laminated structures, laminated veneer lumber, reinforced I-beams, parallel strand lumber, reinforced particle board, and ladders. The use of a thermoplastic polyurethane, particularly the high Tg thermoplastic polyurethane as the impregnating resin provides a means of recycling and reusing the reinforced lumber, as well as shaping the composite in ways that would be impossible using conventional fibe-reinforced thermoset composites.

CROSS-REFERENCE STATEMENT

This application is a divisional of and claims the benefit of U.S.Utility application Ser. No. 09/876,633, filed Jun. 7, 2001 (now issuedas U.S. Pat. No. 6,592,962), and further claims the benefit of U.S.Provisional Application No. 60/233,879, filed Sep. 20, 2000 and U.S.Provisional Application No. 60/210566, filed Jun. 9, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to wood that is reinforced with afiber-reinforced thermoplastic composite.

As a result of dwindling stocks of high quality lumber, wood productengineers have had to adopt innovative designs to enhance the structuralproperties and reduce the cost of wood products. Examples of thesedesigns include glue laminated wood beams, laminated veneer lumber,parallel strand lumber laminated wood columns, wood I-beams, and woodtrusses. However, merely redesigning the lumber products has not provedadequate. Therefore, efforts have continued to combine low quality, lowcost lumber with structurally reinforcing composites to achieve the sameperformance as achieved with higher cost, higher quality wood products.

For example, O'Brien in U.S. Pat. No. 5,026,593 discloses the use of athin flat aluminum strip to reinforce a laminated beam. O'Brien teachesthat the aluminum strip must be continuous across the width and lengthof the beam and that the reinforcing strip may be affixed to thelowermost lamina to improve tensile strength or to theuppermost laminato improve compression strength of the beam.

In U.S. Pat. No. 5,362,545, Tingley (hereinafter “Tingley '545”)discloses the use of reinforced plastics in glue laminated wood beams(glulams). More particularly, Tingley '545 discloses the use ofpultruded composites as materials. These composites are prepared byimpregnating thermoset or thermoplastic resins into a continuous fiberbundle. The disclosed thermoset resins include epoxy resins, polyesters,vinyl esters, phenolic resins, polyimides, and polystyrylpyridine whilethe thermoplastic resins include polyethylene terephthalate andnylon-66. The preferred fibers are disclosed as being aramid or carbonfibers or high modulus polyethylene fibers. Tingley '545 discloses thatit is necessary to “hair up” the surface of the fiber-reinforcedcomposite so that fibers protrude, thereby providing a means of adheringthe wood to the composite without having to use expensive epoxyadhesives.

In U.S. Pat. No. 5,498,460, Tingley discloses improved adhesion of thefiber-reinforced composite to the wood by creating multiple recessesdistributed over the opposed major surfaces of the composite.

In U.S. Pat. No. 5,547,729, Tingley discloses abraded or haired upsynthetic tension and compression reinforcements to provide enhancedtensile and compression strength.

In U.S. Pat. No. 5,641,553, Tingley discloses a reinforcing panelcomprising a plurality of substantially continuous and parallelsynthetic fibers, affixed to at least one cellulose surface material,which improves adhesion of the panel to a wood structure.

In U.S. Pat. No. 5,885,685, Tingley discloses an aramid fiber matencased in resin along with the fiber-reinforced composite to reduceinterlaminar shear failure when nonepoxy resins are used for encasement.

In U.S. Pat. No. 6,037,049, Tingley discloses a composite that comprisestwo types of fiber strands encased in a resin matrix, a high strengthfiber for the central portion of the composite and a lower strengthfiber for the edges. The use of lower cost fibers along the edgesreduces waste during a planing process.

In each instance, the prior art requires some kind of modification tothe surface of the composite to enhance adhesion to the wood member. Itwould therefore be desirable to prepare a glue-laminated wood structuralmember that is reinforced with a composite that adhered to wood eitherwith reduced or no adhesive and without surface modification of thecomposite.

SUMMARY OF THE INVENTION

The present invention addresses a problem in the art by providing areinforced wood structure comprising an a) elongated multilamellar woodmember having an uppermost lamina with an outer surface, a lowermostlamina with an outer surface, a longitudinal center, and a transversecenter; and b) a first elongated fiber-reinforced thermoplasticcomposite layer disposed 1) through the longitudinal center of the woodmember; and 2) between and adherent to the major surfaces of two of thelaminae, or adherent to the outer surface of the uppermost or thelowermost lamina; wherein the composite contains a plurality ofsubstantially parallel continuous fibers impregnated with athermoplastic polymer having the following structural units:

where Z is S or O, and Z′ is S, O, N-alkyl or NH.

In a second aspect, the present invention is a reinforced wood structurecomprising a) an elongated multilamellar wood member having an uppermostlamina with an outer surface, a lamina adjacent to the uppermost lamina,a lowermost lamina with an outer surface, and a lamina adjacent to thelowermost lamina; b) a first elongated fiber-reinforced thermoplasticcomposite layer disposed through the length of the wood member andbetween and adherent to the uppermost lamina and the lamina adjacent tothe uppermost lamina; c) a second elongated fiber-reinforcedthermoplastic composite layer disposed through the longitudinal centerof the wood member and between and adherent to the lowermost lamina andthe lamina adjacent to the lowermost lamina, wherein the compositelayers each contain a plurality of substantially parallel continuousfibers impregnated with a thermoplastic polyurethane.

In a third aspect, the present invention is a reinforced wood structurecomprising a fiber reinforced thermoplastic composite layer disposedonto wood or dispersed into wood particles, wherein the thermoplasticcomposite layer contains a plurality of substantially parallelcontinuous fibers impregnated with a thermoplastic polymer having; thefollowing structural units:

where Z is S or O, and Z′ is S, O, N-alkyl or NH.

In a fourth aspect, the present invention is a reinforced wood structurecomprising a first fiber-reinforced thermoplastic composite flange and asecond fiber-reinforced thermoplastic composite flange, each flangebeing bonded to a web to form a reinforced I-beam, wherein thefiber-reinforced thermoplastic composite flanges contain a plurality ofsubstantially parallel continuous fibers impregnated with athermoplastic polymer having the following structural units:

where Z is S or O, and Z′ is S, O, N-alkyl or NH.

In a fifth aspect, the present invention is a reinforced wood structurecomprising an elongated multilamellar wood member having a longitudinalcenter, a transverse center, a width center, and a plurality ofelongated fiber-reinforced thermoplastic composite rods, at least two ofwhich rods are tension reinforcement rods and at least two of which rodsare compression reinforcement rods, wherein the tension reinforcementrods are disposed through the longitudinal center, and distal on eitherside of the width center and imbedded into and adhering to a laminadistal from the transverse center and proximal to the lowermost laminaof the multilamellar structure, and wherein the compressionreinforcement rods are disposed through the longitudinal center, anddistal from either side of the width center and imbedded into andadhering to a lamina distal from the transverse center and proximal tothe uppermost lamina of the multilamellar structure.

In a sixth aspect, the present invention is a reinforced wood structurecomprising a wood member having slots or bores and a plurality ofelongated fiber-reinforced thermoplastic composite rods incorporatedinto the slots or bores of the wood member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is an illustration of a reinforced glue-laminated or laminatedveneer lumber structure.

FIG. 1b is an illustration of a glue-laminated or laminated veneerlumber structure that is reinforced with a plurality of composite rods.

FIG. 1c is an illustration of reinforcing composite rods disposed in theslots of a slotted lamina.

FIG. 1d is an illustration of reinforcing composite rods disposed in thebores of a bored lamina.

FIG. 2 is an illustration of a reinforced I-beam.

FIG. 3 is an illustration of an I-beam reinforced with purelysynthetically reinforced flanges.

FIG. 4 is an illustration of particle board reinforced with strands ofsynthetic reinforcement.

FIG. 5 is an illustration of a wood particle structure reinforced withsheets of synthetic reinforcement.

FIG. 6 is an illustration of a glum lam reinforced with sheets ofsynthetic reinforcement in a zig zag pattern.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment of the present invention, FIG. 1a shows anelongated glue laminated wood structural member 10 having multiple woodlaminae 12 that are bonded together as elongated boards. The woodstructural member 10 is shown with its ends supported by a pair ofblocks 14 and bearing a point load 16 midway between the blocks 14. Itwill be appreciated that the glue laminated wood member 10 could alsobear loads distributed in other ways (for example, cantilevered) or beused as a truss, joist, or column. It will also be appreciated that thewood member 10 can be in the form of laminated veneer lumber (LVL).

Under the conditions represented in FIG. 1a, the lowermost lamina 12 ais subjected to a substantially pure tensile stress and the uppermostlamina 12 d is subjected to a substantially pure compressive stress. Toincrease the tensile load-bearing capacity of the glue laminated woodmember 10, at least one layer of synthetic tension reinforcement 24 isoffset from the transverse center 25 and adhered between lamina proximalto the lowermost lamina 12 a, preferably between the lowermost lamina 12a and the adjacent lamina 12 b. Alternatively, the synthetic tensionreinforcement 24 may be adhered to the outer surface 28 of the lowermostlamina 12 a.

To increase the compressive load-bearing capacity of the glue laminatedwood member 10, at least one layer of synthetic compressionreinforcement 30 is distal from the transverse center 25 and adheredbetween lamina proximal to the uppermost lamina 12 d, preferably betweenthe uppermost lamina 12 d and the adjacent lamina 12 c. Alternatively,the synthetic compression reinforcement 30 may be adhered to the outersurface 34 of the uppermost lamina 12 d.

Synthetic tension reinforcement 24 and synthetic compressionreinforcement 30 are generally positioned through the longitudinalcenter 16 and preferably extend along from about 20% to about 100% ofthe length of the wood structural member 10. If the length of thesynthetic tension reinforcement 24 is less than the length of the woodstructural member, a pair of spacers 35, preferably wood spacers, areadvantageously positioned at opposite ends of synthetic tensionreinforcement 24 between laminae 12 a and 12 b to maintain a uniformseparation therebetween. Similarly, a pair of spacers 35 areadvantageously positioned at opposite ends of synthetic compressionreinforcement 30 between laminae 12 c and 12 d to maintain a uniformseparation therebetween.

The widths x of the synthetic reinforcements 24 and 30 are preferablymatched to the finished width x′ of wood member 10 by methods such asthose described in U.S. Pat. No. 5,456,781, column 4, lines 8-35, whichteachings are incorporated herein by reference. The thicknesses z of thereinforcements 24 and 30 are application dependent but are preferably inthe range of from about 0.01 cm, more preferably from about 0.1 cm, topreferably about 1 cm, more preferably to about 0.5 cm.

FIG. 1b illustrates a modification of the embodiment illustrated in FIG.1a, wherein the multi-lamellar structure 10 is reinforced with aplurality of synthetic reinforcement rods incorporated into two of thelamina of the multi-lamellar structure 10 and along the grain of thestructure 10. Although FIG. 1b illustrates a composite with twosynthetic tension reinforcement rods 24 a, and two synthetic compressionreinforcement rods 30 a, it is possible, and may be desirable, toincorporate a multitude of synthetic tension and compressionreinforcement rods into the composite. Synthetic reinforcing sheets canbe used in place of or in addition to reinforcing rods and the syntheticreinforcement rods (24 a, 30 a) may be mechanically or adhesively bondedor mechanically and adhesively bonded to the lamellae.

The synthetic tension reinforcement rods 24 a are disposed through thelongitudinal center 16 of the structure and may, but do not necessarily,extend through the length of the structure 10. The rods 24 a are distalfrom either side of the width center 31 and embedded into and bonded toa lamina distal from the transverse center and proximal to the lowermostlamina 12 a, preferably imbedded into and bonded to the lowermost lamina12 a, which may be slotted or bored to accommodate to the tensionreinforcement rods 24 a.

Similarly the two synthetic compression reinforcement rods 30 a aredisposed through the longitudinal center 16 of the structure 10, and mayextend through the length of the structure 10. The rods 30 a are distalfrom either side of the width center 31 and imbedded into and bonded toa lamina distal from the transverse center 25 and proximal to theuppermost lamina 12 d, preferably imbedded into and bonded to theuppermost lamina 12 d, which may be slotted or bored to accommodate tothe compression reinforcement rods 30 a. FIG. 1c illustrates a portionof an individual slotted lamina 12 a with the rods 24 a disposed in theslots. FIG. 1d illustrates a portion of an individual bored lamina 12 awith the rods 24 a disposed in the bores.

The reinforced multilamellar structure represented by FIG. 1b isespecially advantageous for applications requiring repairing orreinforcing existing structures such as bridges and utility poles, orupgrading beams in houses, because of the ease of incorporating the rodsinto these structures. Other structures suitable for reinforcement usingthis embodiment include home and office furniture such as bookshelves,kitchen cabinet shelves, work surfaces, and desks. To simplifymanufacture of structures such as glulam beams, a separate lamstockconsisting of only the layer of a glulam containing reinforcement, or alamstock consisting of a layer of LVL containing reinforcement can bemade and supplied separately.

The composite rods can have any desirable cross-sectional shape such ascircular, oval, rectangular, and star-shaped, and the rods may behollow, C-shaped, Z-shaped, and the like. The rods are desirablyincorporated through the longitudinal center of the multilamellarstructure, and preferably along the entire length of the structure.

Another example of a use for the reinforced wood structures illustratedin FIGS. 1 and 2 is wood ladders containing linear veneer lumber railsthat are reinforced with composite rods or sheets.

FIG. 2 represents another embodiment of the reinforced wood structure 10of the present invention which is generally in the shape of an I-beam.The embodiment depicts a compression reinforcement portion 40 (alsoknown as a compression flange) at the top of the wood structure 10 and atension reinforcement portion 42 (also know as a tension flange) at thebottom of the wood structure 10. The compression flange 40 comprises asynthetic compression reinforcement 30 bonded between the uppermostlamina 12 d and the adjacent Laconia 12 c. The tension reinforcementflange 42 comprises the synthetic tension reinforcement 24 bondedbetween the lowermost lamina 12 a and the adjacent lamina 12 b. A web 44is centrally disposed between the reinforcement flanges 40 and 42 attheir major surfaces 50 and 54 to form the “I” beam shape. The web 44,which can be any suitable material, but is preferably made of orientedstrand board or plywood. The web 44 has substantially the same length asthe laminae 12 a, 12 b, 12 c, and 12 d, but is narrower in width. Theratio of the width x of the reinforcement flanges 40 and 42 to the widthy of the aligned web 44 is application dependent but generally variesfrom about 4:1 to about 10:1. It is to be understood that thereinforcement flanges 40 and 42 may contain several wood laminae. Inthis case, the synthetic reinforcements 24 and 30 can be bonded betweenany two laminae. Alternatively, the synthetic reinforcements can bebonded to a major surface 50, 52, 54, or 56 of the reinforcement flanges40 and 42. In this case, the reinforcement portions may contain a singlelamina or multiple laminae.

Reinforcement of wood can also be accomplished by shaping the syntheticreinforcements in the form of flanges to adhere to the web without woodlaminae. FIG. 3 illustrates such a reinforcement. In FIG. 3A a syntheticcompression reinforcement flange 31 is depicted as adhering to the top45 and major surfaces 47 and 49 of the aligned web 44 while a synthetictension reinforcement flange 25 is depicted as adhering to the bottom 51and the major surfaces 47 and 49 of the web 44. Alternatively, asillustrated, in FIG. 3B, the tension reinforcement flange 25 can beadhered to the major surfaces 47 and 49 of web 44 without being adheredto the bottom 51, while the compression reinforcement flange 31 can beadhered to the major surfaces 47 and 49 of the web 44 without beingadhered to the top.

Synthetic reinforcement can also be used to improve the physicalproperties of adherent wood particles such as particle board, orientedstrand board, oriented strand lumber, fiberboard, and chipboard. Asillustrated in FIG. 4, particle board 60 is reinforced with strands ofsynthetic reinforcement 62 dispersed in an aligned or random fashion inthe particle board 60. The dimensions of the synthetic reinforcementstrands 62 can vary widely, but are typically in the order of 0.01 cm×01cm×1 cm to about 0.1×0.5×10 cm. Because of the unique properties of thesynthetic reinforcement material, discussed herein, this reinforcedparticle board is recyclable and reusable. Indeed, the reinforcedstructural lumber illustrated in FIGS. 1-3 can all be recycled to makereinforced particle board 60. To our knowledge, no other syntheticreinforcement is suitable for this purpose.

FIG. 5 illustrates another embodiment of the present invention. In thisembodiment, a reinforced wood particle structure 61 can be made bysuperposing sheets of synthetic reinforcement 63 onto one major surfaceof elongated particle board beam 65 and preferably opposing majorsurfaces of elongated particle board beam 65. The reinforcing fibers 67are longitudinally aligned and extend continuously through the length ofthe reinforced wood particle structure 61. This reinforced wood particlestructure 61, which is similar in strength and stiffness to LVL or solidlumber, can be manufactured in a single stage because the adhesive usedto bind the particles together to make the particle board (typicallyMDI) can also adhere the composite to the particle board as it is beingmanufactured. The reinforced wood particle structure 61 can also be inthe shape of a panel, or an I-beam, wherein the synthetic reinforcementsuperposes outer major surfaces of flanges made from particle board.

In another embodiment of the present invention, strands of the syntheticreinforcement material can be incorporated into parallel strand lumber(PSL) in which strands of lumber are aligned along an axis. In thisembodiment, the synthetic reinforcement material is aligned along thesame axis as the lumber strands and dispersed through the PSL structure.

FIG. 6 illustrates another embodiment of the invention. In thisembodiment, sheets of the synthetic reinforcement 40 are incorporated ina zig-zag fashion across the grain of the multilamellar structure 10.The sheets can be inserted into an appropriately slotted structure.

The preferred synthetic reinforcements and flanges depicted in FIGS. 1-6are fiber-reinforced thermoplastic composites described by Edwards etal. in U.S. Pat. No. 5,891,560, column 3, lines 8-37 to column 4, lines1-35, which description is incorporated herein by reference. Thepreferred fiber-reinforced composite comprises a depolymerizable andrepolymerizable thermoplastic polymer resin, and at least 30 percent,more preferably at least 50 percent, and most preferably at least 65percent by volume of substantially parallel reinforcing fibers that areimpregnated by the polymer resin and extend substantially through thelength of the resin. The composite is preferably prepared by pultrusionas described by Edwards et al. to form the synthetic reinforcement ofthe desired length, width, thickness, and shape.

The preferred class of polymers for the fiber-reinforced composite aredepolymerizable and repolymerizable polymers (DRTPs) having thefollowing structural units:

where Z is S or O, preferably O, and Z′ is S, O, N-alkyl or NH,preferably O or NH, most preferably O. As used herein, the termdepolymerizable and repolymerizable refers to a polymer the undergoessome degree of molecular weight reduction upon application of asufficient amount of heat, and some degree of molecular weightrebuilding when the polymer is cooled.

The reinforcing fibers are not critical to the practice of the presentinvention and may include glass, carbon, aramid fibers, ceramic, andvarious metals. The DRTP is a single- or two-phase polymer that can beprepared by the reaction of: a) a diisocyanate or a diisothiocyanate,preferably a diisocyanate; b) a low molecular weight compound (not morethan 300 Daltons) having two active hydrogen groups; and c) optionally ahigh molecular weight compound (molecular weight in the range of fromabout 500 to about 8000 Daltons) with two active hydrogen groups. Thelow molecular weight compound, in combination with the diisocyanate ordiisothiocyanate group, contributes to what is known as the “hardsegment” content. Similarly, the high molecular weight compound, incombination with the diisocyanate or diisothiocyanate group, contributesto what is known as the “soft segment” content. Either a stoichiometricamount or a stoichiometric excess of the diisocyanate can be reactedwith the low molecular weight compound and optionally the high molecularweight compound. Preferred DRTPs are thermoplastic polyurethanes andthermoplastic polyureas, preferably thermoplastic polyurethanes.

As used herein, the term “active hydrogen group” refers to a group thatreacts with an isocyanate or isothiocyanate group as shown:

where Z and Z′ are previously defined, and R and R′ are connectinggroups, which may be aliphatic, aromatic, or cycloaliphatic, orcombinations thereof. Examples of, compounds with two active hydrogengroups include diols, diamine, dithiols, hydroxyamines, thiolamines, orhydroxythiols. Preferred compounds with two active hydrogen groups arediols.

A preferred class of thermoplastic polyurethanes is polyurethaneengineering thermoplastic resins, also known as rigid thermoplasticpolyurethanes (RTPUs). RTPUs are characterized by having a glasstransition temperature (T_(g)) of not less than 50° C. RTPUs preferablyhave a hard segment not less than about 75 percent by weight, morepreferably not less than 90 percent by weight, to about 100 percent byweight, based on the weight of the RTPU. The disclosure and preparationof polyurethane engineering thermoplastic resins is described, forexample, in Goldwasser et al. in U.S. Pat. No. 4,376,834, and Oriani inU.S. Pat. No. 5,627,254, which teachings are incorporated herein byreference. Such resins are commercially available under the trade nameISOPLAST™ engineering thermoplastic polyurethanes (a trademark of TheDow Chemical Company).

Another preferred class of thermoplastic polyurethanes is softthermoplastic polyurethane resins (STPUs). STPUs are characterized byhaving a T_(g) of less than 25° C. Preferably, the STPU has a hardsegment of not less than 15 and not more than 50 weight percent, and asoft segment of not more than 85, and not less than 50 weight percent,based on the weight of the STPU. STPUs are commercially available underthe trade name PELLETHANE™ resins. It is to be understood that blends ofSTPUs and RTPUs can also be used as a resin for the fiber-reinforcedthermoplastic composite.

Processes for the manufacture of glue-laminated structural wood members,LVL, I-joists and PSL are well known in the art. See, for example, U.S.Pat. No. 5,4556,781, column 3, lines 27-49, incorporated herein byreference. The conventional processes can be modified to incorporatesynthetic tension reinforcement or synthetic compression reinforcementor both.

One of the advantages of using pultruded fiber-reinforced compositesmade using thermoplastic polyurethanes is that the formation ofdiisocyanates in the depolymerization process provides a mechanism foradhesion to wood without surface modification of the wood laminae,without the use of an ancillary adhesive, and without modification ofthe surface of the fiber-reinforced composite. This natural ability ofthe composite to adhere to wood is due presumably to the presence ofactive hydrogens in the wood. Thus, the thermoplastic composite part canbe bonded to wood, or affixed between two lamina to provide synthetictension or compression reinforcement or both by heat bonding the part tothe surfaces of the wood laminae. An alternative or additionalexplanation for the propensity of the thermoplastic matrix to bond tothe wood is that under melt producing conditions, the matrix can flowinto the cracks and pores of the wood, thereby producing mechanicalbonding.

Nevertheless, it may be desirable and preferable in some instances touse an ancillary adhesive such as those generally used in the woodindustry, for example, phenol formaldehyde, phenol resorcinolformaldehyde, or MDI, to promote adhesion between the wood laminae andthe thermoplastic composite part. Generally, the amount of adhesiverequired is less than the amount required for typical matrix resins dueto the natural tendency of the thermoplastic polyurethane to chemicallyand/or mechanically bond to wood.

Alternatively, or additionally, it may be desirable to react thecompound or compounds having two active hydrogen groups with astoichiometric excess of the diisocyanate or diisothiocyanate to createan “overindexed” DRTP, which more readily reacts with the activehydrogens in the wood.

The reinforced lumber of the present invention shows surprisingadvantages in hygrothermal cycling due to perpendicular compliance, andimproved toughness for handling in lamination mills due to the uniquenature of the resin used to make the fiber-reinforced thermoplasticcomposite. This composite does not produce undesirable VOCs duringmanufacture, and it can be prepared at rapid line speeds as compared tothe pultruded composites that do not use these unique resins.Furthermore, the depolymerizable/repolymerizable nature of theengineering thermoplastic polyurethane resin provides extremely highmodulus composites (greater than 40 GPa) as compared to otherfiber-reinforced thermoplastic composites, thus resulting in superiorreinforcement of the wood. Moreover, the thermoplastic nature of thecomposite provides an avenue for the shaping of and hammering nails intothe composite, which are not possible using fiber-reinforced thermosetcomposites due to their brittleness. Finally, the unique nature of thiscomposite provides a means to recycle and reuse the reinforced lumber,which is not possible using conventional fiber-reinforced thermoset orthermoplastic composites.

What is claimed is:
 1. A reinforced wood structure comprising at leastone elongated fiber-reinforced thermoplastic composite rod embedded intoat least one wood member.
 2. The reinforced wood structure of claim 1wherein one wood member has a plurality of slots or bores and aplurality of elongated fiber-reinforced thermoplastic composite rodsembedded into slots or bores along the grain of the wood member.
 3. Thereinforced wood structure of claim 2 wherein the thermoplastic polymeris an engineering thermoplastic polyurethane having a Tg of not lessthan 50° C.
 4. The reinforced wood structure of claim 1 which iselongated and multilamellar, wherein the rods are disposed through themultilamellar structure in a zig-zag fashion across the grain of thelamellae and through the length of the wood structure.
 5. The reinforcedwood structure of claim 1 wherein the composite rods contain athermoplastic polymer having the following structural units:

where Z is S or O, and Z′ is S, O, N-alkyl or NH.
 6. A reinforced woodstructure comprising an elongated multilamellar wood member having alongitudinal center, a transverse center, a width center, and aplurality of elongated fiber-reinforced thermoplastic composite rods, atleast two of which rods are tension reinforcement rods and at least twoof which rods are compression reinforcement rods, wherein the tensionreinforcement rods are disposed through the longitudinal center, anddistal on either side of the width center and imbedded into and adheringto a lamina distal from the transverse center and proximal to thelowermost lamina of the multilamellar structure, and wherein thecompression reinforcement rods are disposed through the longitudinalcenter, and distal from either side of the width center and imbeddedinto and adhering to a lamina distal from the transverse center andproximal to the uppermost lamina of the multilamellar structure.
 7. Thereinforced wood structure of claim 6 wherein the composite rods containa thermoplastic polymer having the following structural units:

where Z is S or O, and Z′ is S, O, N-alkyl or NH.
 8. The reinforced woodstructure of claim 7 wherein the thermoplastic polymer is an engineeringthermoplastic polyurethane having a Tg of not less than 50° C.
 9. Thereinforced wood structure of claim 8 wherein the lowermost lamina andthe uppermost lamina each have slots or bores, and the tensionreinforcement rods are imbedded into and adhering to the slots or boresof the lowermost lamina, and the compression reinforcement rods areimbedded into and adhering to the slots or bores of the uppermostlamina.
 10. The reinforced wood structure of claim 8 wherein the tensionand compression reinforcement rods do not extend through the length ofthe structure.
 11. The reinforced wood structure of claim 8 wherein thetension and compression reinforcement rods extend through the length ofthe structure.